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SUMMARY:IMX talk - Two-dimensional coherent spectroscopy for composite col
 lective excitations
DTSTART:20260310T111500
DTEND:20260310T121500
DTSTAMP:20260404T153640Z
UID:2262215a2ce024d343a9380788a4f77cfa4580a1131dc19a274accbc
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Bruce Normand\, Paul Scherrer Institute\nUnlocking the non
 linear response of quantum materials is key to technological advances in h
 igh-frequency and low-power electronics\, spintronics and quantum informat
 ion processing. Massive advances in the technology of shaping ultrafast an
 d ultra-intense laser pulses over wide frequency ranges have enabled the c
 reation of many nonequilibrium phenomena whose origins lie in nonlinear pr
 ocesses. One of the most promising approaches to the ultrafast control of 
 collective excitations in quantum materials is magnetophononics\, which co
 mbines coherent driving of lattice excitations by ultrashort THz pulses wi
 th the intrinsic spin-lattice coupling to create a nonequilibrium magnetic
  response. To separate and analyze all of the high-order response features
  in a magnetophononic system\, we apply two-dimensional coherent spectrosc
 opy (2DCS) to the minimal model of an alternating spin chain coupled to on
 e Einstein phonon by performing pump-pump-probe calculations at all time d
 elays. The resulting complete map of the intrinsic nonlinear dynamics incl
 udes at first order composite phonon-bitriplon hybrid excitations\, second
 -order peaks at the sum and difference frequencies of these mutually repel
 ling hybrids and multiple third-order response peaks corresponding to the 
 characteristic 2Q\, NR\, PP and R processes of 2DCS. The composite nature 
 of magnetophononic excitations is reflected in a selection of streak featu
 res\, most notably strong antidiagonal streaks at the rephasing peaks\, wh
 ose origin lies in the availability of elementary magnetic excitations ove
 r a continuum of energies. To stress the ubiquity of streaks in 2DCS as th
 e fingerprint of intrinsic continuum dynamics\, which goes far beyond conv
 entional disorder interpretations\, we compute 2DCS spectra for the strong
 ly spin-phonon-coupled insulating quantum magnet CuGeO$_3$ and demonstrate
  extensive streaking at the R and NR peaks for multiple driven phonon mode
 s.\n 
LOCATION:BM 5202 https://plan.epfl.ch/?room==BM%205202
STATUS:CONFIRMED
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